1. Field of the Invention
The present invention relates to an ink ribbon cassette for storing an ink ribbon and a printing apparatus.
2. Description of the Related Art
In recent years, printing apparatuses have been widely used with which a photographic print can be easily acquired from image data obtained by using a digital camera. A thermal transfer printing apparatus using a thermal head is known as one of these printing apparatuses. A thermal transfer recording method using a thermal head causes a thermal head and a platen roller to convey an ink ribbon made of a long film, and a recording sheet while nipping the ink ribbon and the recording sheet, thereby performing printing. The ink ribbon is formed by applying dyes (inks) to the long film. On the thermal head, a plurality of heating elements (resistive elements) is arranged in a line. By selectively energizing these heating elements, the dyes applied to the ink ribbon are transferred onto the recording sheet, thereby performing the printing.
In such a thermal transfer printing apparatus, if the ink ribbon is not stably conveyed, wrinkles are generated in the ink ribbon. If wrinkles are generated in the ink ribbon, color loss occurs when printing is performed. To address this problem, in Japanese Patent Application Laid-Open No. 2-178074, a rotating shaft deformed into an arcuate shape is brought into contact with an ink ribbon, thereby generating a force that stretches the ink ribbon in the width direction. The force can prevent the generation of wrinkles in the ink ribbon.
If, however, the rotating shaft is used by deforming the rotating shaft into an arcuate shape, the shaft needs to be rotatably held while maintaining the arcuate deformation. Thus, the stress caused by the deformation of the shaft is constantly applied to shaft reception portions. Further, if an ink ribbon is conveyed without applying high tension to the ink ribbon, the ink ribbon is conveyed in such a manner that only the vicinity of the center of the rotating shaft is deformed to have an arcuate shape and comes into contact with the ink ribbon, while both ends of the ink ribbon in the width direction are not in contact with the rotating shaft. This also creates a new problem in that an imbalance in the tension applied to the ribbon in the width direction is likely to generate wrinkles.